Application of N,N′-ethylenebis(acetylacetoneiminato) Nickel (II) and Copper (II) Schiff Base Complexes as Acid–Base Sensing Materials and Indicators in Volumetric Titrations : Qualitative, Spectroscopic and Titrimetric Analyses

Abstract

The objective of the research described herein is to report the applicability of simple Schiff base complexes, [M(L)], where M = Ni(II), Cu(II); L = N,N 0 -ethylenebis(acetylacetoniminate), as sensing materials and indicators in qualitative, spectroscopic and volumetric determinations of acids and bases. In this regard, UV-Vis spectroscopic properties of [M(L)] in the presence of different acids (-0.25 \ pKa \ 5) were investigated, and acid-base titrations using these complexes as indicators were carried out. Alcoholic solutions of [Cu(L)] and [Ni(L)] are purple and orange-red, respectively, and both solutions become decolourized upon adding strong acids (pKa \ 2). During this process, the intensity of the original d-d band (k max * 550 nm) decreases, and new anion-dependent CT (k max [ 700 nm) and anion-independent CT (k max * 310 nm) bands, accompanied by three isobestic points, emerge. Addition of NaOH to the same solution, reproduces both the original colours and UV-Vis spectra, implying that the acid-base chemistry of [M(L)] is reversible. No such colour change occurs upon adding weak acids (pKa [ 4), hence [M(L)] can be used as sensing materials for distinguishing strong acids from weak acids. In strong acid-weak base titrations, [M(L)] complexes are better indicators than methyl orange, as they give very sharp and clearly visible colour changes at the end point. The present paper reports, for the first time, the applicability of N,N 0 -ethylenebis(acetylacetoneiminato) nickel (II) and copper (II) Schiff base complexes as acid-base indicators in strong acid-weak base titrations where the pH at the equivalence point is *4.

Formation constants and thermodynamic parameters of bivalent Co, Ni, Cu and Zn complexes with Schiff base ligand: Experimental and DFT calculations

“…Schiff base ligands are able to coordinate with many different metals and stabilize them in various oxidation states [11][12][13].…”

Evaluation of Antioxidant Activity On Plum Fruit (Prunus domestica L.) Skin Extract Applied For Natural Acid-Base Indicator

“…The indicator of acid-base is a complex compound that can react with acids or bases with a change in color according to the concentration of hydrogen ions through the process of titration (Reshetnyak et al, 2013;Zoromba, 2017;Sukhanov et al, 2016;Petrossyan et al, 2018;Udugala-Ganehenege et al, 2015;Baldigo et al, 2018). Indicators used in strong acid-base titrations are usually synthetic indicators, such as phenolphthalein (PP) indicators.…”

Acid-Base Indicator Paper Extracted from Rose (Rosa damascena Mill) and Asoka Flower (Ixora occinea Linn) Ethanols

“…It is usually used to differentiate acid or base solution by providing different acid or base solutions (Fesseden & Fesseden, 1999). An acid-base indicator is complex compound and can react with acid or base features with colour changes based on the hydrogen ion concentration with titration process (Reshetnyak et al, 2013;Zoromba, 2017;Sukhanov et al, 2016;Petrossyan et al, 2018;Udugala-Ganehenege et al, 2015 ;Baldigo et al, 2018;Akbar, 2019) The function is based on the indicator features. They can provide different colours when they are added to acid or base solutions.…”